Time/Date Axis

[drizzt]

i want to have a timescale with millisecond accuracy, but i don't really know how to do that.
All examples only have second accuracy and always use QDateTime::fromTime_t(int v) or something else.

Has somebody experiences with that and can give me a tip how to solve that problem?

thx

[Lupus]

Hej drizzt.
My idea would be to create a similar type to time_t where you count milliseconds from some start date.
The easiest thing would be to use QDateTime::toTime_t of your start date and multiply it to get your milliseconds and add as many milliseconds as needed for the datapoint
Then you could call

QDateTime t = QDateTime::addMSecs((qint64)v);
return t.toString("yyyy-MM-dd HH:mm:ss:zzz");

in the label function from dinojerm.

Just take care of the really big number which is lager than an interger, so use qint64.
I have NOT tested this, it ist just a suggestion.

[techr]

Hi Phil Winder,
is it possible to get the datetime.zip? looks like the above link does not contain all the files...after i download, i could not unzip it...

Thanks in advance

[Patrik]

I'm very interested in something similar to this. Basically I need only dates as X axis. Do you thing this snippet is correct?

QwtPlot *plt = ui->qwtPlot;
plt->setAxisScaleDraw(QwtPlot::xBottom, new TimeScaleDraw("dd/M/yy"));
QDate date = getDateFromSomewhere();
QDateTime tm(date);
xData.append(tm.toTime_t());
yData.append(someData());

[FelixB]

I'm very interested in something similar to this. Basically I need only dates as X axis. Do you thing this snippet is correct?

why don't you try it by yourself?

[falconium]

Hi Philminder, I tried your example under 6.00-rc5, and it fails at:

..\datetime\mainwindow.cpp: In constructor 'MainWindow::MainWindow(QWidget*)':
..\datetime\mainwindow.cpp:40: error: no matching function for call to 'QwtPlotCurve::setData(double*, double*, int)'
..\libraries\qwt/qwt_plot_seriesitem.h:146: note: candidates are: void QwtPlotSeriesItem<T>::setData(QwtSeriesData<T>*) [with T = QPointF]

It looks like setData arguments have changed...

[corrado1972]

please download latest Qwt (6.0) and recompile: it should works.

[TorAn]

corrado1972 -
I downloaded datetime.zip and curve->setData(&xData[0], &yData[0], xData.size()); (mainwindow.cpp line40) does not compile with Qwt 6.0.0.

setData should be replaced with setRawSamples

[corrado1972]

TorAn excuse me but I understood that the problem was referred to the examples included in Qwt release.
My advice is to discard the datetime.zip and look in the examples, friedberg and cpuplot: there is all the necessary to get datetime axis.
bye